I'm looking for a waterproof under-saddle tool bag. I have a Dahon Mariner: https://goo.gl/PCLeZD

I'd want something that is quick to remove, and that can hold two small adjustable wrenches, 2 tire levers, a nipple wrench, patch kit, chain breaker, and one or two other small items.

Use any saddle bag and a baggie for anything you don't want to get wet. I don't worry about tubes and tire levers or CO2. Tools should be OK also.

Check Nashbar. They sell weatherproof roll-top type dry bags similar to Topeak's.

I use ziplock baggies to protect items inside my Serfas Speed Bag, but the baggies themselves take up space so it's a tight fit when I add more items than usual -- such as a spare USB battery. But I mostly use that on my road bike and try to avoid riding that bike on days with rain risk. I got caught in a downpour last weekend, on the far outskirts of Hurricane Harvey. After 10 miles in the rain everything in ziplock bags in the saddle bag was dry -- wallet, phone, USB battery, etc.

But a weatherproof saddle bag would be handier for my all weather bikes.

I have an Ortlieb in the small size that is waterproof, has a quick release and holds 2 tubes, 2 cartridges, a multi-tool, a lever and an air chuck.

The small is about the size of a regular seat bag. The extra large is big enough to fit everything above plus a vest and arm warmers. I don't recall ever seeing a large.

OP, do you use fenders? I ask because I am not sure I have ever seen significantly wet anything in a standard under the seat toolbag, even on very wet rides when I used them. Even when I have locked the bike outside for mush of a day in that rain. (I've spent the past 32 years riding in the Pacific Northwest year round so I have seen wet.) I could see getting close fitting ziplocs for say batteries (or paper items) but wouldn't sweat the rest. I've never seen enough rust to matter.

There are enough products we buy that have small custom ziplocs that I would just set them aside and use the ones that fit my "must stay dry" items.

You can also use that fabric waterproofing spray from REI. Doesn't do wonders, but for a toolbag that is water resistant to start, it doesn't have to. (I am trusting you never submerge the toolbag.)

Edit: as I was typing this, I thought "contact Ortlieb. They could make it."

Ben

I've been using Jandd for several years and I love them!! Bomb proof. Bicycle Seat Packs BTW, they have a great sale going on now.

Sandwich bag for my multi-tool solved that issue for me. It's the humidity more than rain, just my cheap Nashbar saddle bag seems to keep the rain out.

small dry bag held by a toe-strap?